The invention relates to a sheet feeding apparatus and method. It particularly relates to a method and apparatus for singulating relatively stiff thermographic print media employing a traveling vacuum roller mounted on an outrigger trolley employing a single row of vacuum cups. The arrangement is designed to accomplish feeding of a single sheet of media such as film from a stack of such media without significant relative motion between the sheets that could produce scratching.
Themographic print media is fabricated from a laminate of a substrate, an overlying laminated disposable peel sheet and an intermediate multicomponent image layer of image forming material including adhesives joining the substrate and peel sheet. The substrate has a frangible substrate tab portion formed along a score line, formed in a free surface of the substrate adjacent a marginal edge of the media. The media is difficult to handle for a number of reasons. The material while being pliable is relatively stiff and thus conventional methods for singulating and transporting the material are either impractical or ineffective since the flexed sheets tend to return to their unflexed condition. Also, the tab portion is designed to snap or break along the score line to separate the substrate from the peel sheet. However, until such time as the peeling operation is to be effected, it is important that the laminate remain intact.
There are a number of known methods for feeding single sheets of paper or like media from one location to another. These devices often move one sheet relative to another. This is not a particular concern with paper or other relatively durable media for which surface quality is important but not crucial. However, film media and especially thermographic print media are less pliable than paper, are delicate and require great care in handling, otherwise surface scratches will develop which can adversely effect image resolution. The same fine defect free surfaces necessary for fine resolution, result in interactive forces, e.g., mechanical, chemical and electrical in origin which cause the media when stacked to tend to stick to adjacent sheets, thereby making singulation of such media difficult.